Field
The present invention relates generally to a method for detecting particulate on a substrate, and in particular a method to detect and measure particulate on thin, flexible substrates such as glass sheets or ribbons.
Technical Background
High speed, non-contact methods are needed to identify the occurrence, the locations, the number, the sizes and/or the types of particulates on the surfaces of thin and flexible glass substrates, such as glass sheets or glass ribbons as may be useful for display or other electronic applications. As used herein, the term glass refers typically to silica-based inorganic glasses, but can also refer to non-silica-based glasses, or glasses formed by organic compounds. While glass sheets may be flat and small in size, glass ribbons can be hundreds of meters long, a meter or more wide and suitable for winding onto or unwinding from spools. If particulates on the surface can be detected and identified during substrate manufacturing, then steps can be taken to address the source of the particulates and, if necessary, to clean away the particulates in a downstream process. This can reduce waste material, increase production rates and decrease re-working and cleaning costs. In some products that use the glass as a laminate component, a particle only one micrometer (μm) or less in size can be sufficient to interfere with the bond between the laminated layers. Thus, particles that escape detection can create loss of raw material, add to handling expense and lower the yield of good product for other manufacturers that use the glass as a sub-component.